Multi chromatic thermally sensitive recording medium

Details Multi chromatic thermally sensitive recording medium Multi chromatic thermally sensitive recording medium

2000-10-10

2003-06-17

Hess, Bruce H. (Department: 1774)

Record receiver having plural interactive leaves or a colorless

Having a colorless color-former, developer therefor, or...

Identified organic electron acceptor other than phenolic resin

C503S204000, C503S226000

Reexamination Certificate

active

06579828

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a multi chromatic thermally sensitive recording medium, more in detail relates to a multi chromatic thermally sensitive recording medium having plural color developing layer which develops different color tones by different heating conditions of thermal head.
DESCRIPTION OF THE PRIOR ART
In general, a thermally sensitive recording media having a thermally sensitive color developing layer mainly composed of colorless or pale colored electron donning type dye precursor (hereinafter shortened to dye precursor) and color developer that develops color by reacting with dye precursor when heated, is disclosed in Japanese Patent Publication 45-14035 and is widely used in a commercial scale. As a method for recording of this thermally sensitive recording medium, usually, a thermal printer in which a thermal head is installed is used. This kind of thermal recording method is superior to a conventional recording method from the view point of noiseless at recording process, does not need a developing and fixing processes, maintenance free, equipment is relatively cheap and compact and the obtained image is very clear. Therefore, this method is widely applied in the field of a facsimile or a computer, various kinds of measuring instrument and for a labeling machine along with the growth of an information industry. Along with the expanding of the usage, the required qualities to a thermally sensitive recording medium are becoming more multiplex, for instance, a higher sensitivity, a stabilization of image and a multi coloration of image can be mentioned. Especially, the multi coloration of recorded image have a merit that the letters or patterns to be emphasize can be recorded by a different color tone from the other part.
As a multi chromatic thermally sensitive recording medium, for example, a method to prepare plural color developing layers that develop different colors on a substrate and to form a recording image using variations of heating temperature or thermal energy can be mentioned. The structural feature of said thermally sensitive recording medium is characterized to laminate the layers in order from a higher temperature color developing layer to a lower temperature color developing layers that develops color by lower temperature or lower thermal energy than said higher temperature color developing layer. These multi chromatic thermally sensitive recording media can be mainly divided to two different types, that is, a color discharging type and a color adding type.
The color developing mechanism of the color discharging type is disclosed in e.g. Japanese Patent Publication 50-17865, Japanese Patent Publication 57-14320 or Japanese Patent Laid Open Publication 2-80287. That is, only a lower temperature color developing layer develops color by lower temperature heating, and when heated by higher temperature, the color developed by lower temperature is discharged by the action of color discharging agent having color discharging effect, and only a higher color developing layer develops color. This method has a merit that the desired color tone can be selected voluntarily, however, it is necessary to add large amount of color discharging agent to perform a sufficient color discharging effect. The color discharging type multi chromatic thermally sensitive recording medium have problems, that is, the deterioration of recorded image preservability caused by added large amount of color discharging agent or the deterioration of recording sensitivity caused by a large consumption of thermal energy necessary for melting the achromatic agent.
Meanwhile, as the example of a color adding type thermally sensitive recording medium, the methods disclosed in Japanese Patent Publication 49-27708, Japanese Patent Publication 51-19989 or Japanese Patent Laid Open Publication 51-146239 can be mentioned. That is, the methods to obtain distinguishable two color images by adding different thermal energy to a double layered color developing layer which develops different two colors are disclosed. In the methods disclosed above, a lower temperature developing layer located at the upper position develops color by lower heating temperature, and a higher temperature developing layer located at the bottom position develops color by higher heating temperature, thus both two color developing layers develop colors. And, since in the obtained image these two colors of said two layers are mixed, it is substantially necessary to make the color of the layer located at the bottom position black. Further, since the black color image of bottom layer is obtained by mixing with the color of an upper layer, the color of an upper layer is fogged over the black color image and the difference between said two developed color tones is not so clear. Furthermore, there are problems that when the developed color is exposed to the high temperature atmosphere, for example on a dash board of car, the higher temperature developing layer develops color and a color tone developed by lower temperature becomes fogging or becomes black. In Japanese Patent Laid Open Publication 4-329186, there is a description that the color cloudy problem caused by color developing of a higher temperature color developing layer at the lower temperature heating can be solved by containing specific color indicator in a higher temperature color developing layer. However, this method is not sufficient at the clearness of color tone developed at lower temperature in high temperature atmosphere and the stability of ground color. Still further, recently, the case to use a thermally sensitive recording paper as a receipt becomes more popular, in which case the preservability of recorded image becomes necessary. However, a thermally sensitive recording paper having sufficient image preservability is not yet developed up to the present time.
BRIEF SUMMARY OF THE INVENTION
The object of this invention is to provide a multi chromatic thermally sensitive recording medium that can obtain clear color developed images both at a lower temperature color developing layer and a higher color developing layer, further the obtained color image developed at lower temperature does not become fogging by the color tone of higher temperature color developing layer at the high temperature atmosphere, furthermore the image preservability is excellent.
The present invention is a multi chromatic thermally sensitive recording medium comprising, a higher temperature color developing layer containing dye precursor and an organic color developer that reacts with said dye precursor and develops color by heating, and at least one lower temperature color developing layer that develops different color from that of said higher temperature color developing layer and develops color by lower temperature than the color developing temperature of said higher temperature color developing layer laminated in order on a substrate, wherein an organic color developer contained in said higher temperature color developing layer contains at least one compound selected from the group consisted of diphenylsulfone bridgeable type compound represented by general formula (1), which is disclosed in WO97/16420, and 3-{[(phenylamine)carbonyl]amino}benzenesulfoneamide compound represented by general formula (2), which is disclosed in Japanese Patent Laid Open Publication 8-59603,
wherein, X and Y can be different and indicates a saturate or an unsaturated liner or grafted hydrocarbon group of carbon number 1 to 12 which can possess an ether bond, or
wherein R indicates a methylene group or an ethylene group, T indicates a hydrogen atom or an alkyl group of carbon number 1 to 4, and R
1
to R
6
independently indicate a halogen atom, an alkyl group of carbon number 1 to 6 or an alkenyl group, further m, n, p, q, r, t indicate an integer number of 0 to 4 and when are bigger than 2, R
1
to R
6
can be different and a is an integer of 0 to 10.
Further, in the present invention, the lower temperature color developing layer which develops di

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